1. Institute for Software Technology at the German Aerospace Center (DLR), 38108, Braunschweig, Germany. This work was carried out while this author was a Ph.D. student at the Dipartimento di Ingegneria Civile e Ingegneria Informatica (DCII), Università degli Studi di Roma, “Tor Vegata,” Via del Politecnico 1, 00133, Rome, Italy.
2. Department of Aeronautics, Imperial College London, London SW7 2AZ, UK.
3. Dipartimento di Ingengeria Civile e Ingegneria Informatica, Università degli Studi di Roma, “Tor Vergata,” Via del Politecnico 1, 00133, Rome, Italy.